1. Field of the Invention
The present invention generally relates to an optical disk recording apparatus, and more particularly, to an optical disk recording apparatus that can draw visible characters- and figures on the recording region of an optical disk such as a CD-R disk, a CD-RW disk, and a DVD disk.
2. Description of the Related Art
Optical disks, especially CD-R disks, are rapidly being popularized as recording media to exchange data between personal computers, since the prices of both recording media and recording apparatuses are becoming lower. Additionally, CD-R disks are handy because they can store data that are too large to store on a flexible disk, and can be read by CD-ROM drives that are installed in most personal computers as a standard feature. Furthermore, thanks to recent improvement in recording speed of CD-R drives, a user can store a large amount of data in a CD-R disk in a short period of time.
In a case where a user has hundreds of CD-R disks, the user faces difficulty in identifying and arranging the CD-R disks.
In the case of a so-called stamped CD, a ready-made factory-recorded medium, identification information and contents thereof are printed on the label side of the stamped CD. The user can identify a stamped CD and know its contents based on the printed information.
For example, Japanese Laid-open Patent Application No. 5-6576 discloses an optical disk on which a visible mark is indicated by forming a pit and a method of fabricating the optical disk.
Furthermore, Japanese Laid-open Patent Application No. 11-213455 discloses an optical disk on which a visible mark is indicated by extending the length of a pit.
On the other hand, in the case of CD-R, nothing or only the brand mark of the manufacturer of the CD-R disk is printed. The user cannot identify the CD-R disk or recognize the contents stored in the CD-R disk by looking at the exterior of the CD-R disk.
After storing data therein, the user usually hand-writes identification information such as a title on the label side of the CD-R disk using an oily pen to avoid this problem. In this case, the user needs the oily pen, and the hand-written title does not look nice.
The user may print the identification information on a label dedicated to the CD-R disk and stick the label on the CD-R disk, or print directly on the CD-R disk, if the CD-R disk can retain the printing. The user can print a full-colored beautiful label in this case. The label, however, incurs an additional cost, and the data stored therein may be damaged if the data recording layer of the CD-R disk becomes unstuck together with the label. If the user desires to directly print the identification information on the CD-R disk, the user needs a dedicated printer and a CD-R disk that can retain the printing, which disk costs more than a regular CD-R disk.
Based on the background as described above, a method of indicating the title and the contents of the CD-R disk without using a pen or a dedicated printer is desired.
Data are recorded in a CD-R disk by deforming the recording layer (burning the dye) and substrate (forming “pits”) by a strong laser beam. The data recorded in the CD-R disk are read by applying a weak laser beam to the pits and detecting the change in the light reflected by the pits.
The change in the reflective light heavily depends on the frequency of the laser beam. Because the reflective ratio of visible light is changed by the pits, the color of a portion where data are recorded differs from the color of the other portion.
In the case of a stamped CD, an image formed on the recording side by stamping pits is not visible since the change in reflective ratio is not large enough and contrast is too low. In the case of a CD-R disk, the image formed on the recording side has a contrast large enough for visual recognition.
It is possible to write visual characters and figures on the recording region of the CD-R disk by forming pits using tracks in the recording region.
Conventionally, Japanese Laid-open Patent Application No. 11-134648, for example, has proposed an optical disk recording apparatus that avoids reducing data capacity of the CD-R disk by superimposing the visual image on recorded data. Japanese Laid-open Patent Application No. 11-134648, for example, has further proposed an optical disk recording apparatus that forms a visual image by converting data expressed in rectangular coordinates into data expressed in polar coordinates and changing the pit width in accordance with the data expressed in polar coordinates.
Such conventional optical disk recording apparatuses, however, cannot protect the accuracy of recorded data and cannot provide the contrast required for visual recognition even if the pit width is changed in accordance with the data converted from rectangular coordinates to polar coordinates.